McDonnell Douglas F-15E Strike Eagle

The McDonnell Douglas (now Boeing) F-15E Strike Eagle is an American all-weather multirole strike fighter derived from the McDonnell Douglas F-15 Eagle. The F-15E was designed in the 1980s for long-range, high-speed interdiction without relying on escort or electronic-warfare aircraft. United States Air Force (USAF) F-15E Strike Eagles can be generally distinguished from other US Eagle variants by darker aircraft camouflage, conformal fuel tanks (CFTs) mounted along the engine intake ramps (although CFTs can also be mounted on earlier F-15 variants) and a tandem-seat cockpit.

The Strike Eagle has been deployed for military operations in Iraq, Afghanistan, Syria, and Libya, among others. During these operations, the strike fighter has carried out deep strikes against high-value targets and combat air patrols, and provided close air support for coalition troops. It has also been exported to several countries.

Development

Origins

The McDonnell Douglas F-15 Eagle was introduced by the USAF to replace its fleet of McDonnell Douglas F-4 Phantom IIs. Unlike the F-4, the F-15 was designed for the air superiority mission with little consideration for a ground-attack role; the F-15 Special Project Office opposed the idea of F-15s performing the interdiction mission, giving rise to the phrase "Not a pound for air to ground."Davies and Dildy 2007, pp. 9, 15, 20, 35. In service, the F-15 has been a successful fighter, scoring over 100 aerial combat victories and zero losses in air-to-air combat as of 2007.

Despite a lack of official interest, McDonnell Douglas quietly worked on an F-15-derived interdictor fighter. The company envisaged the aircraft as a replacement for the General Dynamics F-111 and the remaining F-4s, as well as to augment the existing F-15s. In 1978, the USAF initiated the Tactical All-Weather Requirement Study, which looked at McDonnell Douglas's proposal and other options such as the purchase of further F-111Fs. The study recommended the F-15E as the USAF's future strike platform.Donald 1995, p. 42. In 1979, McDonnell Douglas and Hughes began a close collaboration on the development of the F-15E's air-to-ground capabilities.

To assist in the F-15E's development, McDonnell Douglas modified the second TF-15A prototype, AF serial number ''71-0291'', as a demonstrator. The aircraft, known as the Advanced Fighter Capability Demonstrator, first flew on 8 July 1980. It was previously used to test conformal fuel tanks (CFTs), initially designed for the F-15 under the designation "FAST Pack", with ''FAST'' standing for "Fuel and Sensor, Tactical. It was subsequently fitted with a Pave Tack laser designator targeting pod to allow the independent delivery of guided bombs. The demonstrator was displayed at the 1980 Farnborough Airshow.Donald 1995, p. 44.

Enhanced Tactical Fighter

In March 1981, the USAF announced the Enhanced Tactical Fighter program to procure a replacement for the F-111. The program was later renamed the Dual-Role Fighter (DRF) competition. The concept envisioned an aircraft capable of launching deep air interdiction missions without requiring additional support by fighter escort or jamming. General Dynamics submitted the F-16XL, while McDonnell Douglas submitted the F-15E. The Panavia Tornado was also a candidate, but since the aircraft lacked a credible air-superiority fighter capability, coupled with the fact that it was not American-made, it was not seriously considered.

The DRF evaluation team, under the direction of Brigadier General Ronald W. Yates, ran from 1981 through 30 April 1983, during which the F-15E logged more than 200 flights, demonstrated takeoff weight of more than , and validated 16 different weapons-carrying configurations.Donald 1995, p. 45. McDonnell Douglas, to assist ''71-0291'' in the evaluation, added to the program other F-15s, designated ''78-0468'', ''80-0055'', and ''81-0063''. The single-engined F-16XL was a promising design, which with its radically redesigned cranked-delta wing, greatly boosted performance; if selected, the single- and two-seat versions were to be designated F-16E and F-16F, respectively. On 24 February 1984, the USAF chose the F-15E; key factors in the decision were the F-15E's lower development costs compared to the F-16XL (US$270 million versus US$470 million), a belief that the F-15E had future growth potential, and possessing twin-engine redundancy.Jenkins 1998, p. 36.Ciborski, James R
"The F-15 Eagle: A Chronology."
''History Office, Aeronautical Systems Center, Air Force Materiel Command,'' Wright-Patterson AFB, Ohio, June 2002. The USAF was initially expected to procure 400 aircraft, a figure later revised to 392.Ulsamer, Edgar
"In Focus: The Dual-Role Eagle."
''Air Force magazine'', April 1984.

Construction of the first three F-15Es started in July 1985. The first of these, ''86-0183'', made its maiden flight on 11 December 1986. Piloted by Gary Jennings, the aircraft reached a maximum speed of Mach 0.9 and an altitude of 40,000 feet (12,000 m) during the 75-minute flight. This aircraft had the full F-15E avionics suite and the redesigned front fuselage, but not the aft fuselage and the common engine bay. The latter was featured on ''86-0184'', while ''86-0185'' incorporated all the changes of the F-15E from the F-15. On 31 March 1987, the first officially completed F-15E made its first flight.

The first production F-15E was delivered to the 405th Tactical Training Wing, Luke Air Force Base, Arizona, in April 1988. Production continued into the 2000s with 236 produced for the USAF through 2001."Boeing F-15E Eagle."
''Jane's All the World's Aircraft'', Jane's Information Group, 2010 (subscription article, dated 26 February 2010).

Upgrade programs and replacement

The F-15E was upgraded with the Raytheon APG-82 Active Electronically Scanned Array (AESA) radar after 2007, and the first test radar was delivered to Boeing in 2010. It combines the processor of the APG-79 used on the F/A-18E/F Super Hornet with the antenna of the APG-63(V)3 AESA being fitted on the F-15C; it was named APG-63(V)4 until it received the APG-82 designation in 2009. The new radar is to be part of the F-15E Radar Modernization Program, which also includes a wideband radome (enabling operation on more radar frequencies) and environment control and electronic warfare improvements.

Having a sturdier airframe rated for twice the lifetime of earlier variants, the F-15E is expected to remain in service past 2025. , the USAF's F-15E fleet had an average age of 21 years and an average airframe flying time of 6,000 hours. In 2012, the USAF was reportedly considering future options; no replacement for the F-15E is slated. In 2021, Boeing stated that its F-15EX Eagle II aircraft will replace the existing fleet of F-15C Eagle fighters in the USAF, with the option to also begin replacing the F-15E Strike Eagle aircraft. The F-15EX Eagle II follows very closely to the Strike Eagle design, with a two-seat configuration as well as further air to ground capabilities. The USAF has stated that they will look into the F-15EX replacing the Strike Eagles at a later time. Another choice is the F-35 Lightning II, set to replace other aircraft such as the F-16 Falcon; a ''F-35E'' variant was studied. Adding a second seat to the F-35 is complex and costly, especially to preserve its stealth profile; providing for greater range and payload would also be difficult tasks. Alternatively, the role could be covered by a combination of fighter and bomber aircraft, such as the B-21 Raider. The F-15E may also be replaced by a clean-sheet sixth-generation aircraft design.

ALASA

On 24 March 2014, Boeing won a $30.6 million contract from DARPA as part of the Airborne Launch Assist Space Access (ALASA) program. The goal of the program is to cut the cost of putting microsatellites into orbit by 66% through advances in launch systems. Under the 11-month contract, Boeing will build twelve launch vehicles, each with a payload capability up to . An ALASA vehicle is to be fitted under an F-15E, which will climb to 40,000 ft, then be released and fire its four engines to reach low-Earth orbit. Awarding the contract to Boeing would make use of the F-15E as the carriage vehicle, as previous design contracts had been given to Lockheed Martin to use the F-22 Raptor and Virgin Galactic to use their SpaceShip Two aircraft. DARPA had previously insisted they wanted to select an aircraft they would not need to modify heavily to carry and launch the ALASA payload.

Design

The F-15E's deep-strike mission is a radical departure from the original intent of the F-15 since it was designed as an air-superiority fighter under the mantra "not a pound for air-to-ground." The basic airframe, however, proved versatile enough to produce a very capable strike fighter. The F-15E, while designed for ground attack, retains the air-to-air lethality of the F-15, and can defend itself against enemy aircraft.Jenkins 1998, pp. 35–36.

The F-15E prototype was a modification of the two-seat F-15B. Despite its origins, it includes significant structural changes as well as more powerful engines. The aft fuselage was designed to incorporate the more powerful engines with advanced engine bay structures and doors, which incorporate Superplastic forming and diffusion bonding technologies. The back seat is equipped for a weapon systems officer (WSO, pronounced "wizzo") to work the air-to-ground avionics via multiple screens; these view the radar, electronic warfare, or thermographic cameras, monitor aircraft or weapons status and possible threats, select targets, and use an electronic moving map to navigate. Two hand controls are used to select new displays and to refine targeting information; displays can be moved from one screen to another using a menu of display options. Unlike previous two-place jets (e.g. the F-14 Tomcat and Navy variants of the F-4), whose back seat omitted flying controls, the F-15E's back seat is equipped with its own stick and throttle so the WSO can take over flying, albeit with reduced visibility.Davies 2003, pp. 63–64.

For extended range, the F-15E is fitted with two conformal fuel tanks (CFTs) that hug the fuselage to produce lower drag than conventional underwing/underbelly drop tanks. They carry 750 U.S. gallons (2,800 L) of fuel, and house six weapons hardpoints in two rows of three in tandem. Unlike conventional drop tanks, CFTs cannot be jettisoned, thus increased range is a trade-off for increased drag and weight compared to a "clean" configuration.

The tactical electronic warfare system (TEWS) integrates all countermeasures on the craft: radar warning receivers, radar jammer, radar, and chaff/ flare dispensers are all tied to the TEWS to provide comprehensive defense against detection and tracking. This system includes an externally mounted ALQ-131 ECM pod which is carried on the centerline pylon when required. The MIDS Fighter Data Link Terminal, produced by BAE Systems, improves situational awareness and communications capabilities via the Link 16 datalink.

The APG-70 radar allows crews to detect ground targets from longer ranges; one feature is that, after a sweep of a target area, the crew may freeze the air-to-ground map then switch to air-to-air mode to scan for aerial threats. During air-to-surface weapon delivery, the pilot is capable of detecting, targeting, and engaging air-to-air targets while the WSO designates ground targets. The APG-70 is to be replaced by the AN/APG-82(v)1 active electronically scanned array radar, which began flight tests in January 2010 with initial operational capability expected in 2014.

Its inertial navigation system uses a laser gyroscope to continuously monitor the aircraft's position and provide information to the central computer and other systems, including a digital moving map in both cockpits. The low-altitude navigation and targeting infrared for night ( LANTIRN) system is mounted externally under the engine intakes; it allows the aircraft to fly at low altitudes, at night, and in any weather conditions, to attack ground targets with a variety of precision-guided and unguided weapons. The LANTIRN system gives the F-15E exceptional accuracy in weapons delivery day or night and in poor weather, and consists of two pods attached to the exterior of the aircraft. At night, the video picture from the LANTIRN can be projected on the head-up display (HUD), producing an infrared image of the ground.Jenkins 1998, pp. 100–101.

The AN/AAQ-13 navigation pod contains a terrain-following radar which allows the pilot to safely fly at a very low altitude following cues displayed on a HUD; it also can be coupled to the autopilot to provide "hands off" terrain-following capability. This pod also contains a forward-looking infrared system which is projected on the HUD, typically used during nighttime or low-visibility operations. The nav pod is installed beneath the right engine intake. The targeting pod contains a laser designator and a tracking system that mark an enemy for destruction as far away as 10 mi (16 km). Once tracking has started, targeting information is automatically handed off to infrared homing air-to-surface missiles or laser-guided bombs. The targeting pod is mounted beneath the left engine intake; configurations may be either the AN/AAQ-14 Target Pod, AN/AAQ-28 LITENING Target Pod, or the AN/AAQ-33 Sniper Advanced Targeting Pod.

The F-15E carries the most air-to-ground weapons in the USAF inventory. It is also armed with AIM-9 Sidewinders and AIM-120 AMRAAMs, retaining the counter-air capabilities of its Eagle lineage, being fully capable of Offensive-Counter-Air operations. Like the F-15C, it also carries an internally mounted General Electric M61A1 20 mm cannon with 500 rounds, which is effective against enemy aircraft and "soft" ground targets.

Since 2004, South Korean firm LIG Nex1 has been manufacturing the F-15's Head-up display; a total number of 150 HUDs were delivered by 2011."S. Korean Firm Wins Contract To Supply F-15 Displays."
''defensenews.com''. Retrieved: 27 February 2012.Sung-Ki, Jung
"S. Korean Firm Exports Head-Up Display to USAF."
''defensenews.com.'' Retrieved: 27 February 2012. LIG Nex1 had been a participant in the F-15K program as a subcontractor to Rockwell Collins. LIG Nex1 is also preparing to manufacture F-15's new multi-function display and flight control computer. Also since 2004, Korea Aerospace Industries (KAI) has produced the F-15's wings and forward fuselages; in 2008, KAI established another production line for Singapore's F-15SG."F-15/Apache Fuselage Monopolization Program."
''koreaaero.com.'' Retrieved: 27 February 2012. KAI is involved in the design and manufacture of the Conformal Weapons Bay (CWB) for the F-15 Silent Eagle.

The engines used on early aircraft are Pratt & Whitney F100-PW-220. Later batches feature the more powerful P&W F100-PW-229 engines. Saudi Arabian and Israeli aircraft originally used P&W F100-229 engines. In 2008, Saudi Arabia decided to re-engine their F-15S and F-15SA fleets with General Electric F110-GE-129 engines. The South Korean F-15K had two different engines; the first batch are powered by GE F110 engines, while the second batch are powered by P&W F100 engines. The Singapore Air Force equipped their F-15SG fleet with GE F110 engines.

Operational history

United States

The F-15E was first delivered to the U.S. Air Force operational units in 1988.Russian Air Power, Airlife Pub Ltd (1 July 2002), p. 37 The F-15E reached initial operational capability on 30 September 1989 at Seymour Johnson Air Force Base in North Carolina with the 4th Tactical Fighter Wing, 336th Tactical Fighter Squadron.

Gulf War

The F-15E was deployed in response to Iraq's invasion of Kuwait in August 1990 for Operation Desert Shield. The 336th Tactical Fighter Squadron flew to Seeb Air Base in Oman to begin training exercises in anticipation of an Iraqi attack on Saudi Arabia; in December, the 335th and 336th squadrons relocated to Prince Sultan Air Base in Saudi Arabia, closer to Iraq's border. At the start of Operation Desert Storm, 24 F-15Es launched an attack on five fixed Scud installations in western Iraq on 17 January 1991. Missions against Scud sites continued through that night with a second strike of 21 F-15Es. At night-time, F-15Es flew hunter missions over western Iraq, searching for mobile SCUD launchers. By conducting random bombings in suspected areas, it was hoped to deter the Iraqis from setting up for a Scud launch.

On the war's opening night, an F-15E failed to hit a MiG-29 with an AIM-9 Sidewinder; other F-15Es also unsuccessfully engaged this lone MiG-29, which was eventually brought down by a missile of unknown origin."Tim Bennett's War."
''Air Force magazine online,'' January 1993.Davies 2005, pp. 17–24. On 18 January, during a strike against a petrol oil and lubricant plant near Basrah, an F-15E was lost to enemy fire, killing both pilot and WSO. F-15E crews described this mission as the most difficult and dangerous of the war as it was heavily defended by SA-3s, SA-6s, SA-8s and Rolands as well as by anti-aircraft artillery. Two nights later, a second and final F-15E was downed by an Iraqi SA-2; the crew survived and evaded capture for several days and made contact with coalition aircraft, but a rescue was not launched due to security issues over an airman who failed to identify himself with proper codes. The Iraqis later captured both airmen.

F-15Es destroyed 18 Iraqi jets on the ground at Tallil air base using GBU-12s and CBU-87s. On 14 February, an F-15E scored its only air-to-air kill of the war: a Mil Mi-24 helicopter. While responding to a request for help by US Special Forces, five Iraqi helicopters were spotted. The lead F-15E of two, via its FLIR, acquired a helicopter in the process of unloading Iraqi soldiers, and released a GBU-10 bomb. The F-15E crew thought the bomb had missed its target and were preparing to use a Sidewinder when the helicopter was destroyed. The Special Forces team estimated that the Hind was roughly over the ground when the bomb hit its target. As another Coalition bombing operation had commenced, the F-15Es disengaged from combat with the remaining helicopters.

F-15Es struck heavily defended targets throughout Iraq, prioritizing SCUD missile sites. Missions aimed at killing Iraqi President Saddam Hussein were undertaken by F-15Es, bombing several suspected locations. Prior to the ground war, F-15Es flew tank plinking missions against Iraqi vehicles in Kuwait. After 42 days of combat, a cease fire came into effect on 1 March 1991, leading to the creation of Northern and Southern no-fly zones over Iraq.

Operations Southern Watch and Northern Watch

Following Desert Storm, two no-fly zones over Iraq were set up, and enforced typically by US and UK aircraft. In one incident, an attack on up to 600 Kurdish refugees by Iraqi helicopters at Chamchamal, northern Iraq, was observed by a flight of F-15Es. As they were not allowed to open fire, the F-15Es instead conducted several high speed passes as close as possible to the Iraqi helicopters to create severe wake-turbulence, while aiming lasers at the helicopter's cockpits to attempt to blind their crews; this caused the crash of one Hind. Afterwards, USAF leadership ordered F-15Es not to fly below to deter a repetition.Davies 2005, pp. 30–31.

F-15Es of the 391st Fighter Squadron, 492d Fighter Squadron, and 494th Fighter Squadron regularly deployed to Turkey throughout the 1990s. In January 1993, in breach of the ceasefire agreement, Iraqi targets below the 32nd parallel north were attacked; 10 F-15Es conducted a punitive strike days later.Davies 2005, p. 33. Most missions were of a defensive nature, the Strike Eagles carried a flexible range of weapons on a typical mission. AWACS aircraft were in close contact with F-15E crews, who would receive new taskings while airborne and thus could fly unplanned attacks on Iraqi targets. After 1993, no-fly zone violations were minimal as Iraq staged a minor withdrawal; in 1997, Turkey approved the creation of Operation Northern Watch (ONW) and permitted US forces to use the Incirlik air base.

In December 1998, Operation Desert Fox was conducted when Iraq refused UNSCOM inspections. On 28 December 1998, three F-15Es struck an SA-3 tracking radar and optical guidance unit, each dropping two GBU-12 500-pound precision-guided munitions (PGMs). After Desert Fox, Iraq frequently violated the no-fly zones, thus F-15Es conducted several pre-planned retaliatory strikes; in ONW alone, weapons were expended on at least 105 days. Between 24 and 26 January 1999, F-15Es expended several AGM-130s and GBU-12s against SAM sites near Mosul, northern Iraq. They also flew in support of Operation Provide Comfort and Operation Provide Comfort II.

Operations in the Balkans

Operation Deny Flight was a United Nations-enforced no-fly zone over Bosnia and Herzegovina due to the deteriorating situation in the Balkans. In August 1993, F-15Es from 492d and 494th FS deployed to Aviano, Italy. In late 1993, NATO ordered a limited F-15E strike at Udbina airfield, targeting Serbian forces in neighboring Croatia. Eight F-15Es armed with GBU-12s took off to attack an SA-6 anti-aircraft vehicle; the mission was cancelled mid-flight over the application of stringent Rules of Engagement.Davies 2005, p. 43. In December 1993, F-15Es launched to destroy a pair of SA-2s which had fired upon two Royal Navy Sea Harrier FRS 1s.Davies 2005, p. 44. In August 1995, F-15Es of 90th Fighter Squadron were also deployed. The 492d and 494th flew over 2,500 sorties since starting Deny Flight, 2,000 of these by 492d. In August 1995, in support of NATO's Operation Deliberate Force, F-15Es flew strike missions against Serbian armor and logistics around the Bosnian capital, Sarajevo. On 9 September, an F-15E deployed the type's first GBU-15 bomb; dropping nine on Bosnian-Serb ground forces and air defense targets near Banja Luka.

In response to the displacement of Kosovars and the Serbian government's rejection of a NATO ultimatum, Operation Allied Force was launched in March 1999. A total of 26 F-15Es flew the first strikes of Allied Force against Serb surface-to-air-missile sites, anti-aircraft batteries and early warning radar stations. Strike Eagles were deployed to Aviano as well as RAF Lakenheath in the UK. In-theater, F-15Es conducted close air support (CAS) missions, a popular concept within the USAF.Davies 2005, p. 47. Missions typically lasted around 7.5 hours, included two aerial refuelings; F-15Es would carry a mix of air-to-air and air-to-ground munitions to perform both combat air patrol duties as well as strike missions in the same mission. Mobile SAM launchers posed a considerable threat to NATO aircraft and had made successful shoot-downs, most notably of a Lockheed F-117 Nighthawk. In order to strike from increased distances, the F-15E was equipped with the AGM-130, which provided a stand-off strike capability.

Operation Enduring Freedom

Weeks after the in 2001, the 391st Fighter Squadron deployed to Ahmad al-Jaber air base, Kuwait, to support Operation Enduring Freedom during the War in Afghanistan. F-15Es met little resistance during initial missions. On the first night, the main targets were Taliban military structures, supply depots, and al-Qaeda training camps and caves. Both the AGM-130 and GBU-15 bombs were expended; this was the GBU-15's first combat usage. GBU-24s and GBU-28s were used against reinforced targets, command and control centers and cave entrances. F-15Es often operated in pairs alongside pairs of F-16Cs. Within weeks of the start of combat operations, there was a lack of targets to strike as nearly all targets had been already destroyed. The Taliban had access to SA-7 and FIM-92 Stinger portable surface-to-air missiles, posing no threat to most aircraft flying above . Additionally, fixed SAM sites near cities as Mazar-i-Sharif and Bagram were struck early on; Afghanistan had rapidly become a low-threat environment for air operations.Davies 2005, p. 64.

Aircraft commonly flew on-call support missions for allied ground forces, F-15Es usually carried MK-82 and GBU-12 bombs in this role, other weapons were sometimes carried, during one mission a GBU-28, two GBU-24s and six GBU-12s were released. Frequent targets during the rest of the war were individual insurgents, light vehicles and supply convoys; cannon fire was often expended as well as bombs from F-15Es. It was during combat over Afghanistan that four 391st crews conducted the longest fighter mission in history; lasting a total of 15.5 hours, nine of those hours spent flying over the target area. Two F-15Es attacked two Taliban command and control facilities, two buildings suspected of being used by Taliban fighters, and a road block; the F-15Es refueled 12 times during the mission.

On 4 March, another incident known as the Battle of Roberts' Ridge involved several F-15Es performing a CAS mission. Aircraft destroyed a Taliban observation post and responded to nearby enemy mortar fire upon Navy SEAL forces searching for an ambushed MH-47E Chinook in the Shah-i-Kot Valley.Davies 2005, p. 72. Several bombs were dropped as the SEAL team took fire, however one bomb missed due to the aircrew using incorrect coordinates. An MH-47 carrying a rescue team was downed by an RPG while attempting to support the SEALs.Davies 2005, p. 73. Following refueling, the F-15Es dropped a further 11 GBU-12s in coordination with ground forces, and fired their cannons on Taliban forces in close proximity to the survivors of the downed MH-47. F-16s of 18th Fighter Squadron also made strafing passes until cannon ammunition was depleted, then resorting to further bomb drops. The F-15Es suffered technical issues involving both radio and weapon failures, several GBU-12s were dropped before returning to Al Jaber in Kuwait.

Years later, several incidents occurred. On 23 August 2007, a friendly fire incident involved an F-15E mistakenly dropping a bomb on British forces, killing three soldiers; the stated cause was confusion between the air controller and the F-15E on the bombing coordinates. On 13 September 2009, an F-15E shot down a non-responsive MQ-9 Reaper drone over Northern Afghanistan to prevent it entering foreign airspace.

Operation Iraqi Freedom

In late 2002, during tension over suspected Iraqi possession of weapons of mass destruction, the 4th Fighter Wing at Seymour Johnson Air Force Base was ordered to maintain at least one squadron ready to deploy to the Persian Gulf. During January 2003, the 336th was deployed to Al Udeid Air Base, Qatar, in coordination with planners of the Combined Air Operations Center